Cathode for magnetrons



Feb. 5, 1952 C. L. CUCCIA CATHODE FOR MAGNETRONS Filed Aug. 12, 1947 A :Snvenfqr Carmen L. 'uz'cl' BB Clitorneg Patented Feb. 5, 1952 (JATIIODE FOR MAGNETR()NSl Carmen L. Cuccia,l Princeton; N. J.. assignor to Radio Crlmwticn4 oi. America, a. corporation 0.1i Delawarev Application Allgllst'lZ, 1917.,l Serial NQ- 768,245LV 6 Claims.- (Cl. ARIEL-337) This invention relates to component elements for electron discharge devices and more particu larly to supports and mounts for cathode elements and to a method of vassembly thereof.

Electron discharge devices such as vacuum tubes generally utilize an electron emitting element or cathode which may have a variety of forms and is supported in an evacuated envelope in proximity to other electron flow'controlling or collecting elements. 1nvacuum tubes of the magnetron type the cathode is generally surrounded by a solid metallic anode in the form of a block which may have an oblong or circular cross-section. The cathode element in these devices is generally an elongated member in the form of a rod or tubular sleeve coated with elec tron emitting material and is located in a space provided in the anode block. This space between the cathode and the surrounding anode is. known as the interaction space. It is important that structural uniformity be maintained in this .interfaction space and therefore the cathode must be accurately located in the anode block in exact alignment `throughout its length with the walls of the anode block forming this interaction space. At the same time the cathode must also be rigidly held in place.

In. the assembly and manufacture of magnetron tubes of the type mentioned, close tolerances must be observed which entails dimculties in production. True centering of the cathode is one of these dimculties and although various mounts have been proposed, these require several operations and manual adjustments to obtain proper insertion and location of the cathode element.

The primary object of my invention is to improve the mounting and assembly of cathode elements in discharge devices where accurate loca,- tion and centering is of prime importance.

Another object of the invention is to provide a novel construction for cathodes and a mounting thereof.

A feature of the invention is. that assembling time as well as the number of operations required heretofore are considerably reduced.

Another feature of the invention is. that the novel construction permits self-centering of the cathode element without aligning operations and adjustments.

An additionall feature of the invention resides in the simplified method of assembly adapted toA production on a large scale.

Other objects and features will be apparent. from the following description ofthe invention, pointed out in -particularity in. the appended claims and taken in connection with the accompanying drawing in which:

Fig. 1 shows in a top view and a sectional view the disc-shaped collar which is to be attached to a conventional cathode sleeve in accordance with the invention;

Fig. 2 shows also in a top view and a side elevational and partially sectionalized View the conventionaly cathode sleeve without the attach-.- ment ofthe collar;

Fig. 3l shows the assembly of the elements: of Figures 1' and 2 in a jig which is illustrated in cross-section;

Fig. 4 is an enlarged View showing in crosssection the cathode assembly mountedv in asolid body including the heating element inside the cathode sleeve.

The problem in the assembly of the. cathode element is mainly accurate centering in the surrounding structure and to provide a simple. yet sturdy support. The cathode 5 in the form of an elongated metallic sleeveA or tube is provided on one end with a centrally apertured metallic disc or collar 6 in such manner thatthelatter has its plane surfaceperpendicular to the. longitudi-` nal axis of the cathode 5. This canbe accom.- plished in accordance with m-y invention byplacing the cathoder in asolid block 'l serving as a jigr(Fig. 3) in which elongated cylindrical hole 1l is drilled accurately and to a depth which permits the end of the cathode' 5f tov protrude the required length. over a cover 8 of the jig 1 to accommodate the collar 6. The cover 8 is perpendicular to the axis ofthe hole l. A brazing operation secures the collar 6 to the cathode 5.

The collar 6, when attached to thecathodein the manner. stated, has a dual function in that its diametric dimension serves as a lateral locating'means uniform in diameter from the center ofthe cathode 5. and its plane surface normal to the longitudinal axis of the cathode provides a: solid support in alignment with and attached to another planesurface.`

In order to locate as well as mount the assem-x bled cathode, any solid body may be used in which there'isan aperture or a channelv accommodating the'cathodesleeve and a countersunk portion'cone centric with the'aperture or channel and cut to a, diameter which permits close fitting of the collar 6.. Y

In Fig. 4, by way of example,v a, solidzbody i0 is shown for mounting the cathode 5, provldedwlth a channel or aperture Il of larger diameter.'tireur-p, the'cathode 5 and an enlargedv annular recess I2` k4515 which closely ts the collar 6. It will beclearthati as long as the recess I2, which in effect countersinks the channel I I, is concentric With the channel, and the base I2I of the recess I2 is at right angles to the walls of the body I forming the channel, the cathode 5 will be properly centered and supported. Moreover, the cathode may be supported in any solid medium in which a countersunk hole can be drilled cir-machined. In some cases the solid medium may be cast or molded with the proper sized recess and channel. This can be provided in various types of mountings such as metallic inserts often used in magnetron structures, or the anode block may be fitted with a ceramic or any suitable insulating bushing provided with the recess and channel.

It will be noted that the tubular passageway II through insert I0 is of larger diameter than the cathode sleeve 5 so that there is'a`sp'ace provided between these two elements. This reduces heat.

conduction from the sleeye, the only metallic con- .tact being through the washer-like element or collar 6. Thus, heatis conserved and the operation ofthe device becomes more emcient.4

It will be observed that the centering and alignment of the cathode is inherent in the structure. When the cathode is inserted into Athe hole and recess, the collar 6 automatically secures true centering and alignment. For a more rigid support the collar 6 may be welded or brazed to the base of the recess when in a metallic body or cemented to it if it is an insulating medium. In other words, the simple disc-shaped collar functions as a laterally extending supporting means which in any properly dimensioned recess assures concentric location and serves also as a support for the cathode element. Simple machining and brazing operations are required only in the steps of assembly and no `centering adjustments are required after the assembly is completed.

The outer cylindrical Wall of at least that portion of the cathode 5 extending beyond the supporting body I0 is coated with suitable electron emitting material, for supplying electrons to the interaction space between the cathode and the anode of the magnetron or other tube in which the cathode is used. .The heater .wires which indirectly heated cath-A odes generally have may be brought out through the end to which the disc is attached. This is shown in Fig. 4, the wires I4 and I5 being the leads of the heater element It in the cathode sleeve 5, which heater wire may have the conventional insulating coating thereon. The solid body or support III may be made of magnetic material and utilized as a so-called magnetic insert in assisting in the generatonof a magnetic field parallel to the cathode when the cathode is utilized in a magnetron. Such .use is described and claimed in the co-pending application of John S. Donal, Jr., et al., which matured on March 22, 1949, as U. S. Patent No. 2,465,211, Serial No..525,514, filed March 8, 1944, and assigned to the same asignee as the present application.

Utilizing the principle of the collar and cathode sleeve, various modifications may be made in the mounting thereof. The collar may be divided in a radial direction into sectors, each fitting in a proper recess cut in the supporting structure; or the disc-shaped collar may be extended in the longitudinal direction ofthe cathode to form a cyinder of larger diameter than the cathode which may be fitted into various types of supports having guides parallel to the cylindrical surface. of the collar.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specic application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

I claim:

l. A cathode unit for discharge devices comprising a body having a channel therein and an enlarged recess at one end of said channel, an elongated'cathode element of smaller size than said channel having a mounting portion disposed inl said channel and a peripheral electron-emitting portion extending beyond said body, and means for accurately locating and rigidly mounting said cathode element in spaced relation in said channel comprising a collar rigidly mounted on said element with a plane surface thereof perpendicular to the longitudinal axis of said element, said collar being mounted in said enlarged recess with said plane surface abutting the base thereof and a peripheral portion closely fitting the outer wall thereof and being rigidly secured to said body.

2. A cathode unit for discharge devices comprising a metallic body having a cylindrical channel therethrough and an enlarged annular recess at one end of said channel and concentric therewith, an elongated cylindrical metallic cathode sleeve of smaller diameter than said channel having a mounting portion disposed in said channel and a peripheral electron-emitting portion extending beyond said body, and means for accurately centering. and rigidly supporting said cathode sleeve in said channel comprising an apertured metallic disc of the same outer diameter as said recess mounted on said sleeve adjacent the end of said mounting portion with its aperture portion brazed thereto in a plane perpendicular to the longitudinal axis of said sleeve, said disc being mounted in said cylindrical recess with one plane face abutting the base thereof and with its peripheral edge closely fitting the cylindrical Wall thereof and being spot welded to said body.

3. The method of mounting an elongated cylindrical metallic cathode sleeve for discharge devices comprising the steps of positioning one end of said sleeve in a hole in a jig, locating a discshaped metallic collar in said jig around and adjacent one end of said sleeve with the plane of said collar perpendicular to said sleeve, brazing said collar on said sleeve, providing a cylindrical channel in a solid metallic body, counter sinking,r said channel axially at one end to a diameter permitting close fitting of said collar forming thereby a recess concentric to said channel and having a base at right angles thereto, inserting said asembled sleeve and collar in said channel and recess, respectively, with said collar abutting said base,.and spot welding said collar to said body.

4. The method of mounting an elongated cylindrical metallic cathode sleeve for discharge devices comprising the steps of positioning one end of said sleeve in a hole of a jig, locating a discshaped metallic collar in'said jig around and adjacent one end of said sleeve with the plane of said collar perpendicular to said sleeve, brazing said. collar on .said sleeve, then providing acylin-V drical channel of larger diameter than said sleeve in a solid metallic body, countersinking said channel axially at one end to form a concentric annular recess having a diameter permitting clase fitting of said collar therein and a base perpen dicular to the axis of said channel, inserting said assembled sleeve and collar in said channel and recess, respectively, With said collar abutting said base, and spot Welding said collar to said body.

5. The method of mounting an elongated cylindrical metallic element comprising the steps of positioning' one end of said element in a hole in a jig. locating a disc-shaped metallic collar in said jig around and adjacent one end of said element with the plane of said collar perpendicular to said element, brazing said collar on said element, providing a cylindrical channel in a solid metallic body, countersinking said channel axially atone end to a diameter permitting close tting of said collar forming thereby a recess concentric to said channel and having a base at right angles thereto, inserting said assembled element and collar in said channel and recess, respec tively, with said collar abutting said base, and spot welding said collar to said body.

6. The method of mounting an elongated cylin drical metallic element comprising the steps of positioning one end of said element in a hole of a jig, locating a disc-shaped metallic collar in said jig around and adjacent one end of said element with the plane of said collar perpendicular to said element, brazing said collar on said element, then providing a cylindrical channel of larger diameter than said element in a solid metallic body, countersinking said channel axial ly at one end to form a concentric annular recess having a diameter permitting close fitting of said collar therein and a base perpendicular to the axis of said channel, inserting said assembled element and collar in said channel and recess, respectively, with said collar abutting said base, and spot welding said collar to said body.

CARMEN L. CUCCIA.

REFERENCES' CITED The following references are of record in the ie of this patent:

UNITED STATES PATENTS Number Name Date 1,422,312 Smith July 11, 1922 1,898,487 Hurley Feb. 21, 1933 2,006,459 Jones et al July 2, 1935 2,185,807r Gabor et al Jan. 2, 1940 2,402,029 Dinnick et al June 11, 1946 FOREIGN PATENTS Number Country Y Date 356,978 Great Britain Sept. 1,7, 1931 

